Johan De Mey

Objective. To investigate dynamic shuttle-mode xenon (Xe)-enhanced dual-energy CT (Xe-DECT) imaging for a regional assessment of ventilation in in vivo rabbit lungs. Approach. Four mechanically ventilated rabbits were scanned during the washout of a 70% xenon in 30% oxygen gas mixture using dynamic shuttle-mode DECT at baseline and during methacholine (MCh)-induced bronchoconstriction (post-MCh). Material decomposition was applied to generate xenon and tissue density images (mg ml ⁻¹ ). A tissue-based correction was used to isolate the xenon concentration ( C _Xe ) in the gas phase of the xenon density images. The resultant C _Xe images were used to investigate regional ventilation defects (VDs) by comparing the VD fraction (VDF, expressed as percentage) between baseline and post-MCh conditions. Additionally, regional ventilation efficiency within the VDs and surrounding (non-VD) areas was quantified as specific ventilation ( s V ˙ in min ⁻¹ ). Ventilation was also qualitatively assessed by evaluating ventilation distributions during washout. Main results. MCh-induced bronchoconstriction resulted in an increase in VDF. The average VDF at baseline was 13.8 ± 8.5%, compared to an average post-MCh VDF of 29.6 ± 7.7%, p = 0.026. The VDs at baseline did not reveal a reduced ventilation efficiency ( s V ˙ V D : 8.4 ± 2.7 min ⁻¹ ), compared to non-VD areas ( s V ˙ n o n − V D : 7.0 ± 3.1 min ⁻¹ ), p = 0.306. In contrast, MCh-induced VDs were found to have a reduced ventilation efficiency ( s V ˙ V D : 4.9 ± 2.3 min ⁻¹ ), compared to non-VD areas ( s V ˙ n o n − V D : 6.4 ± 2.3 min ⁻¹ ), p = 0.004 . Significance. Dynamic shuttle-mode Xe-DECT during washout enabled regional evaluation of ventilation in healthy and pathological in vivo rabbit lungs. As traditional lung function tests offer only global assessments of respiratory impairment, there is a growing interest in pulmonary functional imaging to enable quantitative evaluation of regional lung function.

Purpose: CT‐derived fractional‐flow‐reserve (FFR_CT) is recommended for determining the indication of revascularization. Consensus on optimal fractional‐flow‐reserve (FFR) measurement methods and lesions is lacking. To investigate the diagnostic accuracy of FFR_CT measurement methods for predicting revascularization and factors affecting FFR_CT measurement methods.Methods: A total of 340 patients (382 vessels) who underwent CT angiography and showed ≥50% diameter stenosis (DS) on invasive coronary angiography were evaluated. Enrolled vessels were classified into four groups according to lesion length (focal, CT was measured at the distal end of the vessel (vessel‐distal FFR_CT), distal to the stenotic lesion (lesion‐specific FFR_CT), and trans‐lesion FFR_CT (ΔFFR_CT) and compared with DS. Vessel morphology and left ventricular mass were assessed.Results: In focal lesions, the predictive ability for revascularization of ΔFFR_CT (AUC = 0.71) was comparable to that of DS (AUC = 0.76, p = 0.166) and higher than that of lesion‐specific FFR_CT (AUC = 0.67, p < 0.001) and vessel‐distal FFR_CT (AUC = 0.63, p < 0.001). Multivariable analysis showed that lesion length was the strongest predictor of ΔFFR_CT (β‐coefficient = 0.42, p = 0.006). In diffuse lesions, the predictive ability for revascularization of ΔFFR_CT (AUC = 0.73) was comparable to that of DS (AUC = 0.77, p = 0.667), lesion‐specific FFR_CT (AUC = 0.72, p = 0.653), and vessel‐distal FFR_CT (AUC = 0.69, p = 0.242). Multivariable analysis showed that lesion length was the strongest predictor of ΔFFR_CT (β‐coefficient = 0.99, p < 0.001).Conclusion: The predictive performance of ΔFFR_CT for revascularization was similar to DS in focal and diffuse lesions. ΔFFR_CT was influenced by lesion length.

L/P ratio, which indicates the proportion of lumen volume to plaque volume of the vessel, is lower in lesion than in per-lesion (RCA, 0.9 vs. 7.7; LAD, 1.4 vs. 8.1; and LCX, 0.9 vs. 8.0). For lesion located in the middle segments of the three major vessels, FFR_CT drops from 0.97 to 0.78 for RCA, from 0.94 to 0.55 for LAD, and from 0.99 to 0.72 for LCX, respectively. Invasive coronary angiography shows moderate stenosis in the middle segment of the RCA but no significant obstructive coronary disease at the sites where FFR_CT showed a substantial decline in the LAD and LCX. CCTA indicates coronary CT angiography; ICA, invasive coronary angiography; LAD, left anterior descending artery; LCX, left circumflex artery; RCA, right coronary artery; SOCAD, significant obstructive coronary disease.

The growing popularity of AI has increased its widespread adoption in medicine. However, the relationship between AI and medical experts’ opinions remains elusive. This study investigated the consistency between Random Forest’s prediction for rectal cancer regression grades and doctors’ opinion based on clinical data. We examined the impact of grading system subjectivity on the algorithm. Analyzing clinical parameters and medical notes from 85 rectal cancer patients, we identified patients with ambivalent grades, the “gray-zone patients”, and explored the algorithm’s difficulty in predicting their regression grade. We also introduced a regularization parameter to test if some patients could still correctly be predicted when some statistical information is suppressed. Our results demonstrated that the gray-zone patients were significantly more difficult to classify using the algorithm, suggesting that such patients should be reviewed twice to reduce errors. Additionally, we observed that the regularization parameter did not benefit gray-zone patients as much as others. Our findings emphasize the need for AI and clinical experts to work collaboratively since the algorithm cannot consider the subjectivity that medical experts can identify. Further research is necessary to incorporate subjectivity into AI algorithms to enhance their predictive capabilities and further bridge the gap between medicine and AI.

Portable chest radiography is a valuable tool in the intensive care unit. However, the supine position causes superposition of anatomical structures resulting in less reliable detection of certain abnormalities. Recently, a portable digital tomosynthesis (pDTS) prototype with a modified motorized x-ray device was developed. We aimed to compare the diagnostic value of pDTS to standard bedside chest radiography in the diagnosis of a posterior pneumothorax. A modified motorized x-ray device was developed to perform 15 radiographic projections while translating the x-ray tube 25 cm (10 cm ramp up and 15 cm during x-ray exposure) with a total radiation dose of 0.54 mSv. This new technique of pDTS was performed in addition to standard bedside chest x-ray in a patient with a confirmed posterior hydropneumothorax. The images were compared with the standard bedside chest x-ray and computed tomography (CT) images by two experienced radiologists. The posterior hydropneumothorax previously identified with CT was visible on tomosynthesis images but not with standard bedside imaging. Combining the digital tomosynthesis technique with the portable x-ray machine could increase the diagnostic value of bedside chest radiography for the diagnosis of posterior pneumothoraces while avoiding intrahospital transport and limiting radiation exposure compared to CT.

Background and Aims: In patients with three-vessel disease and/or left main disease, selecting revascularization strategy based on coronary computed tomography angiography (CCTA) has a high level of virtual agreement with treatment decisions based on invasive coronary angiography (ICA).Methods: In this study, coronary artery bypass grafting (CABG) procedures were planned based on CCTA without knowledge of ICA. The CABG strategy was recommended by a central core laboratory assessing the anatomy and functionality of the coronary circulation. The primary feasibility endpoint was the percentage of operations performed without access to the ICA. The primary safety endpoint was graft patency on 30-day follow-up CCTA. Secondary endpoints included topographical adequacy of grafting, major adverse cardiac and cerebrovascular (MACCE), and major bleeding events at 30 days. The study was considered positive if the lower boundary of confidence intervals (CI) for feasibility was ≥75% (NCT04142021).Results: The study enrolled 114 patients with a mean (standard deviation) anatomical SYNTAX score and Society of Thoracic Surgery score of 43.6 (15.3) and 0.81 (0.63), respectively. Unblinding ICA was required in one case yielding a feasibility of 99.1% (95% CI 95.2%–100%). The concordance and agreement in revascularization planning between the ICA- and CCTA-Heart Teams was 82.9% with a moderate kappa of 0.58 (95% CI 0.50–0.66) and between the CCTA-Heart Team and actual treatment was 83.7% with a substantial kappa of 0.61 (95% CI 0.53–0.68). The 30-day follow-up CCTA in 102 patients (91.9%) showed an anastomosis patency rate of 92.6%, whilst MACCE was 7.2% and major bleeding 2.7%.Conclusions: CABG guided by CCTA is feasible and has an acceptable safety profile in a selected population of complex coronary artery disease.

To achieve personalized and optimized treatment for rectal cancer patients, accurate predictions of treatment response based on pre-treatment medical images are essential. However, these images often have varying settings. Our study examined the impact of standardizing pixel spacing and slice thickness on predictive accuracy in medical image analysis. Using our custom-built Evolutionary Random Subspace Forest algorithm, we investigated how altering these spatial settings affected the accuracy of tumor regression grade prediction. We examined 16 different adjustments to spacing settings in CT images taken from 139 rectal cancer patients. Furthermore, we explored a Bayesian approach within our random forest algorithm.We utilized the modified data as prior information and employed radiomics data from the same CT images as posterior information. This study revealed that these alterations notably improved both training and validation accuracy, where the Bayesian approach enhanced model generalization, indicating a close alignment between training and validation results.

Purpose: To assess the performance of the inferior lateral ventricle (ILV) to hippocampal (Hip) volume ratio on brain MRI, for Alzheimer’s disease (AD) diagnostics, comparing it to individual automated ILV and hippocampal volumes, and visual medial temporal lobe atrophy (MTA) consensus ratings. Methods: One-hundred-twelve subjects (mean age ± SD, 66.85 ± 13.64 years) with varying degrees of cognitive decline underwent MRI using a Philips Ingenia 3T. The MTA scale by Scheltens, rated on coronal 3D T1-weighted images, was determined by three experienced radiologists, blinded to diagnosis and sex. Automated volumetry was computed by icobrain dm (v. 5.10) for total, left, right hippocampal, and ILV volumes. The ILV/Hip ratio, defined as the percentage ratio between ILV and hippocampal volumes, was calculated and compared against a normative reference population (n = 1903). Inter-rater agreement, association, classification accuracy, and clinical interpretability on patient level were reported. Results: Visual MTA scores showed excellent inter-rater agreement. Ordinal logistic regression and correlation analyses demonstrated robust associations between automated brain segmentations and visual MTA ratings, with the ILV/Hip ratio consistently outperforming individual hippocampal and ILV volumes. Pairwise classification accuracy showed good performance without statistically significant differences between the ILV/Hip ratio and visual MTA across disease stages, indicating potential interchangeability. Comparison to the normative population and clinical interpretability assessments showed commensurability in classifying MTA “severity” between visual MTA and ILV/Hip ratio measurements. Conclusion: The ILV/Hip ratio shows the highest correlation to visual MTA, in comparison to automated individual ILV and hippocampal volumes, offering standardized measures for diagnostic support in different stages of cognitive decline.